3D Cone-beam Computed Tomography Research Articles

Assessment of sexual dimorphism using 3D CBCT image data among Indians.

It is of interest to investigate the use of frontal sinus morphology, bizygomatic and intermaxillary distance for the determination of gender using Cone-Beam Computer Tomography (CBCT). The study population consisted of 75 subjects (35 females and 40 males) with a mean age of 39.25 years (range: 20-70 years), of ethnic group of south-Indian based population. The data was categorized into three age groups of 20-35, 36-50 and ≥ 50 years. All the features and measurements are recorded for each case using CBCT images that were acquired with a CBCT scanner (Planmeca Mid Proface Cone Beam 3D, Helsinki Finland). The data were subjected to a discriminant functional analysis, compared and statistically analyzed. No two persons had the same measurements. Statistically significant differences were found in the frequency of overall metric parameters between the two genders (P < 0.05) except intermaxillary distance (P = -0.034) respectively. These data provide a valuable tool in differentiating gender. It should be noted that bizygomatic distance can significantly improve the gender determination using discriminant analysis. Cone beam computed tomography is a safe procedure with minimal radiation exposure proved to be highly accurate in sinus imaging and provide irreplaceable and precise information about frontal sinus and the whole skull. Measurements showed significant difference except intermaxillary distance and intersinus width among the three age groups. The discriminant analysis showed that the ability of frontal sinus parameters and bizygomatic distance to identify gender with high accuracy.

Dental age estimation of Malaysian children: a comparison of two-dimensional versus three-dimensional imaging analyses of the developing root apices

Aim This study compared the effectiveness of the three-dimensional (3D) cone beam computed tomography (CBCT) method of age estimation developed by Asif et al. with two-dimensional Cameriere’s method. Subjects and methods CBCT images belonging to 129 Malaysian Chinese and Malay ethnic groups aged 7–14 years were investigated and analysed. Results The results indicated a strong correlation between chronological age and the predictor variables for both Cameriere’s (r = 0.984) and Asif’s (r = 0.988) methods of age estimation. Fisher Z test analysis indicated no statistically significant difference in the correlation values between the two methods. Mean absolute error (MAE) value of 0.613 was observed for Cameriere’s and 0.290 was observed for Asif’s method. Conclusions The results indicated that the methods of age estimation from both Asif et al. and Cameriere et al. are applicable on Malaysian children. However, Asif et al.’s 3D CBCT method of age estimation resulted in greater accuracy and reliability in estimating chronological age.

Head and neck cancer patient positioning using synthetic CT data in MRI-only radiation therapy.

PurposeThe accuracy and precision of patient positioning is crucial in radiotherapy; however, there are no publications available using synthetic computed tomography (sCT) that evaluate rotations in head and neck (H&N) patients positioning or the effect of translation and rotation combined. The aim of this work was to evaluate the differences between using sCT with the CT for 2D‐ and 3D‐patient positioning in a magnetic resonance imaging (MRI)‐only workflow.MethodsThis study included 14 H&N cancer patients, with generated sCT data (MRI Planner v2.2) and the CT deformably registered to the MRI. Patient positioning was evaluated by comparing sCT against CT data: 3D cone beam CT (CBCT) was registered to the deformed CT (dCT) and sCT in six degrees of freedom (DoF) with a rigid auto‐registration algorithm and bone threshold, and 2D deformed digital reconstructed radiographs (dDRR) and synthetic DRRs (sDRR) were manually registered to orthogonal projections in five DoF by six blinded observers. The difference in displacement in all DoF were calculated for dCT and sCT, as well as for dDRR and sDRR. The interobserver variation was evaluated by separate application of the paired dDRR and sDRR registration matrices to the original coordinates of the planning target volume (PTV) structures and calculation of the Euclidean distance between the corresponding points. The Dice similarity coefficient (DSC) was calculated between dDRR/sDRR‐registered PTVs.ResultsThe mean difference in patient positioning using CBCT was <0.7 mm and <0.3° and using orthogonal projections <0.4 mm and <0.2° in all directions. The maximum Euclidean distance was 5.1 mm, the corresponding mean (1SD) Euclidean distance and mean DSC were 3.5 ± 0.7 mm and 0.93, respectively.ConclusionsThis study shows that the sCT‐based patient positioning gives a comparable result with that based on CT images, allowing sCT to replace CT as reference for patient treatment positioning.

Surgically assisted rapid palatal expansion (SARPE): three-dimensional superimposition on cranial base.

To evaluate dental and skeletal changes caused by surgically assisted rapid palatal expansion (SARPE) using the superimposition of three-dimensional cone-beam computed tomography (CBCT) images on the cranial base. This is a retrospective quasi-experiment before-and-after study using a convenience sample. Twenty-four adult patients (13 male and 11 female) were evaluated before SARPE (T0), immediately after expansion (T1), and after 6months of retention (T2). CBCT scans were superimposed on the anterior cranial base using voxel-based registration. Measurements from different reference points were used for comparisons between times. At T1, all teeth had significant buccal tipping. At T2, most teeth remained in the same position as at T1, except the first premolar and the first molar, whose buccal roots moved slightly. The amount of bony expansion was 65 to 70% of the amount of tooth movement. The A point and maxillary incisors moved anteriorly from T0 to T1 and T2 (p < 0.0001). Inter-nasal distance had increased significantly at T1 (p < 0.0001) and remained stable at T2 (p = 0.478). No expansion was achieved at the zygomatic arch (p = 0.114). SARPE promoted substantial buccal tipping of posterior teeth and some bone displacement; it also moved the maxilla and teeth forward and increased nasal width. No other clinical studies have evaluated dental and skeletal changes caused by SARPE using superimposition of 3D CBCT images on the cranial base. This study findings may help clinical dentists plan treatments using safe and reliable information.

Comparative Assessment of the Efficacy of Two-Dimensional Digital Intraoral Radiography to Three-Dimensional Cone Beam Computed Tomography in the Diagnosis of Periapical Pathologies.

Background:Periapical intraoral radiographs are useful in assessing periapical pathologies; essential information often is not extracted owing to difficult interpretation and two-dimensional presentation of three-dimensional structures focusing on using cone beam CT (CBCT) and other advanced imaging modalities.Aims:The present study was conducted to comparatively assess the digital intraoral radiography to CBCT in the diagnosis of periapical pathologies.Materials and Methods:In 50 teeth, CBCT and digital imaging were compared in assessing periapical pathologies using CBCTPA and six-point scoring. The scores obtained were assessed and compared with statistical evaluation. The data were expressed in percentage and number and mean and standard deviation. The level of significance was kept at P < 0.05.Results:On comparing 3D CBCT and 2D digital imaging for assessing the study parameters, it was seen that resorption was seen in 33, 30, and 9 teeth, respectively, on 3, 2, and 1 rooted tooth on CBCT and 13, 16, and 7 teeth on digital radiography. The numbers of roots and root canals on CBCT were 45, 34, and 18 in 3, 2, and 1 rooted tooth and 50, 32, and 18 on digital imaging. Lesions were detected on CBCT in 16, 18, and 18 teeth on CBCT in 3, 2, and 1 rooted tooth, respectively, and in 14, 14, and 16 teeth on digital imaging. Comparing the five-point scale for lesions and CBPAI index for CBCT and digital imaging, the difference was statistically significant with P = 0.004 and <0.0001, respectively.Conclusion:The present study concludes that 3D CBCT is superior in accuracy to 2D imaging in diagnosing the periapical lesions, especially concerning multirooted teeth. Owing to its high radiation exposure and cost, 2D imaging can be incorporated in assessing periapical pathology for the single-rooted tooth.

Tooth segmentation in 3D cone-beam CT images using deep convolutional neural network

Segmentation of an individual tooth in dental radiographs has great significance in the process of orthodontics surgeries and dentistry. Machine learning techniques, especially deep convolutional neural networks can play a key role in revolutionizing the way orthodontics surgeons and dentists work. Lately, many researchers have been working on tooth segmentation in 3D volumetric dental scans with a great degree of success, but to the best of our knowledge, there is no pretrained neural network available publicly for performing tooth segmentation in 3D cone-beam dental CT scans. The methods which so far have been proposed by the researchers in this domain are based on complex multistep pipelines. This lack of the availability of a pre-trained model blocks the path for further explorations in this domain. In this research, we have produced a deep learning model for tooth segmentation from CBCT dental radiographs. The proposed model can segment teeth in CBCT scans in a single step. To train the proposed model, we obtained a dataset consisting of 70 3D CBCT volumes from a local health facility. We labeled the ground truth through a semi-automatic method and trained our neural network. The training yielded a validation accuracy of 95.57% on a binary class semantic segmentation of the 3D CBCT volumes. The model is successfully able to segment teeth, regardless of their type from the background in a single step. This eliminates the need of having a complex and lengthy pipeline which many researchers have been proposing. The proposed model can be extended by incorporating labeling schemes. The custom labeling schemes will help healthcare professionals to perform the labeling as per their needs. The produced model can also provide a basis for further research in this domain.

Comparison of mandibular buccal shelf bone characteristics between two facial types using cone beam computed tomography.

Mandibular buccal shelf (MBS) offers good quality and quantity of bone for orthodontic bone screw (OBS) insertion. Despite several reports of treated patients, there are numerous variables in selecting the exact placement site for OBS placement in the MBS. There are also anatomical variations in this area which must be considered. This study aims to measure and compare the MBS bone characteristics for OBS placement using cone beam computed tomography (CBCT) between two different facial types. Eighty CBCT samples were collected (40 samples of group A horizontal growers and 40 of group B vertical growers). Each CBCT image was reconstructed and oriented with CS 3D CBCT software. The cortical bone thickness, the slope of the MBS, and buccolingual inclination of mandibular second molar were measured and analysed. Cortical bone thickness among horizontal growers was 5.23 ± 0.58 mm and among vertical growers was 4.85 ± 0.37 mm. The slope of MBS among horizontal growers was 60.83 ± 6.15 degrees and among vertical growers was 66.75 ± 6.27 degrees. In both the parameters there was a statistically significant difference between the groups. There was no significant difference between the groups for the buccolingual inclination of 2nd molar. Increased cortical bone thickness and the flatter slope of MBS at the 2nd molar region allows for easier placement of OBS in horizontal growers than in vertical growers.

The prevalence and characteristics of external cervical resorption based on cone-beam computed tomographic imaging: a cross-sectional study.

This study investigated the prevalence and characteristics of external cervical resorption (ECR) regarding sex, age, tooth, stages of progression, and portal of entry, using cone-beam computed tomography (CBCT) scans. CBCT scans of 1,313 patients from a Brazilian subpopulation comprising 883 female and 430 male patients (mean age, 55.2 years), acquired using a PreXion 3D CBCT unit, were evaluated. All permanent teeth included in the scans were evaluated for the presence of ECR according to the 3-dimensional classification and the portal of entry. The association between the presence of ECR and the factors studied was assessed using the χ2 test. Intra-observer agreement was analyzed with the kappa test (α = 0.05). In total, 6,240 teeth were analyzed, of which 84 (1.35%) were affected by ECR. A significant association was found between the presence of ECR and sex, with a higher prevalence in male patients (p = 0.002). The most frequently affected teeth were the mandibular and maxillary central incisors. The most common height was the mid-third of the root. For the portal of entry, 44% of cases were on the proximal surfaces, 40.5% on the lingual/palatal surface and 15.5% on the buccal surface. Intra-observer agreement was excellent. The prevalence of ECR was 1.35%, with a higher prevalence in male patients and a wide age distribution. The mandibular and maxillary central incisors were the most commonly affected teeth, and cases of ECR most frequently showed a height into the mid-third of the root and proximal entry.

Transcarotid access for remote robotic endovascular neurointerventions: a cadaveric proof-of-concept study.

The purpose of this proof-of-concept study was to demonstrate the setup and feasibility of transcarotid access for remote robotic neurointerventions in a cadaveric model. The interventional procedures were performed in a fresh-frozen cadaveric model using an endovascular robotic system and a robotic angiography imaging system. A prototype remote, robotic-drive system with an ethernet-based network connectivity and audio-video communication system was used to drive the robotic system remotely. After surgical exposure of the common carotid artery in a cadaveric model, an 8-Fr arterial was inserted and anchored. A telescopic guiding sheath and catheter/microcatheter combination was modified to account for the "workable" length with the CorPath GRX robotic system using transcarotid access. To simulate a carotid stenting procedure, a 0.014-inch wire was advanced robotically to the extracranial internal carotid artery. After confirming the wire position and anatomy by angiography, a self-expandable rapid exchange nitinol stent was loaded into the robotic cassette, advanced, and then deployed robotically across the carotid bifurcation. To simulate an endovascular stroke recanalization procedure, a 0.014-inch wire was advanced into the proximal middle cerebral artery with robotic assistance. A modified 2.95-Fr delivery microcatheter (Velocity, Penumbra Inc.) was loaded into the robotic cassette and positioned. After robotic retraction of the wire, it was switched manually to a mechanical thrombectomy device (Solitaire X, Medtronic). The stentriever was then advanced robotically into the end of the microcatheter. After robotic unfolding and short microcatheter retraction, the microcatheter was manually removed and the stent retriever was extracted using robotic assistance. During intravascular navigation, the device position was guided by 2D angiography and confirmed by 3D cone-beam CT angiography. In this proof-of-concept cadaver study, the authors demonstrated the setup and technical feasibility of transcarotid access for remote robot-assisted neurointerventions such as carotid artery stenting and mechanical thrombectomy. Using transcarotid access, catheter length modifications were necessary to achieve "working length" compatibility with the current-generation CorPath GRX robotic system. While further improvements in dedicated robotic solutions for neurointerventions and next-generation thrombectomy devices are necessary, the transcarotid approach provides a direct, relatively rapid access route to the brain for delivering remote stroke treatment.

Estimating the Entrance Surface Dose in the Eyes, Thyroid, and Parotid Gland Regions in Adult and Pediatric Groups: A Cone-Beam Computed Tomography Technique

Purpose: This study aimed to determine the Entrance Surface Dose (ESD) of sensitive organs in Cone-Beam Computed Tomography (CBCT) imaging of the maxillofacial region in the two age groups of adult and pediatric. Materials and Methods: In this work, the measurements were performed using Thermo Luminescent Dosimeters (TLD-GR200). The imaging was performed using a PROMAX 3D CBCT scanner for 30 adults and 20 pediatric patients. The ESD value for each patient in the region of eyes, thyroid, and parotid glands was measured by 15 TLDs during CBCT of maxillofacial. Results: The highest and lowest mean values of ESDs were related to the parotid and thyroid gland regions in adults, 4.77 ± 0.61 mGy and 0.37 ± 0.16 mGy, respectively. In addition, these values were obtained 2.97 ± 0.36 mGy and 0.35 ± 0.12 mGy in pediatric groups as the highest and lowest values in that order. The results showed that the ESD values of the parotid gland regions in maxilla and mandible examinations had a significant difference (P &lt;0.05). In addition, there was a significant difference between the ESD values of the parotid gland regions among the adults and pediatric groups (P &lt;0.05). Conclusion: According to the results, the ESD values in both age groups were higher in the parotid gland region during maxillofacial CBCT examinations. Therefore, it is recommended to set radiation parameters like mAs as low as possible for reducing the patient dose, especially pediatric patients due to the more sensitive organs.

The Spheno-Occipital Synchondrosis and Morphometry of Sella Turcica Association with Different Phenotype Factors Related to Ectopic Eye Tooth/Teeth

Objectives: This study investigates the prevalence of Spheno-Occipital Synchondrosis (SOS) and sella turcica morphometry (STM) association with different phenotype factors related to ectopic eye tooth/teeth (EET) using cone beam computed tomography (CBCT) imaging. Methods: This comparative retrospective study analyzed 252 CBCT images. Subjects in the EET group consisted of 197 CBCT images with the phenotype factor in number, i.e., unilateral (13, n = 62; 23, n = 59) or bilateral (1323, n = 76) and matched control (n = 55). SOS and STM were investigated using 3D OnDemand Software. Seven parameters of STM were measured. To test the association X2 used for SOS prevalence, disparities in STM were tested using ANOVA and post hoc Tukey test. Results: The prevalence of unfused SOS was 48.4% and 16.1% in the 1323 and control groups, respectively. Fused SOS prevalence was quite similar in all four groups. Phenotype factor in number, i.e., unilateral 13, 23, or bilateral EET group showed significant disparities in six out of seven parameters (p = 0.044 to p ≥ 0.001). Additionally, phenotype factor in position, i.e., occlusal, buccal, or palatal group showed insignificant disparities (p = 0.463 to p = 1.00). Conclusion: SOS in the ectopic eye tooth group (EETG) was prevalent in the 1323 and buccal position groups. Differing from previous two-dimensional (2D) studies, there were statistically significant disparities in all seven measured variables of STM among control, and three different phenotype factors in numbers were revealed using three-dimensional (3D) CBCT imaging.

The enlargement of the maxillary ostium after balloon sinuplasty evaluated by a novel measuring technique from 3D CBCT images

Our aim was to evaluate the effects of balloon sinuplasty on the size of the ostium in the maxillary sinuses in patients with chronic rhinosinusitis from cone beam computer tomography (CBCT) scans of the sinus. This is a blinded retrospective trial in patients who had undergone balloon sinuplasty of the maxillary sinus. CBCT scans were taken and SNOT-22 Quality of Life questionnaire completed before and 12 months after the operation. The size of the maxillary ostium was measured from the CBCT scans three-dimensionally. The association of changes in the SNOT-22 scores of the ostium was analysed. We discovered that the balloon sinuplasty increased the size of the maxillary ostium in all dimensions. The changes were statistically significant (p<0.05) in the axial diameter and the ostium area. The number of patent ostia increased after the intervention. The association between SNOT-22 score and ostium patency were statistically significant before the operation. Our conclusion is that the threedimensional measuring technique provides a reliable method to evaluate ostium dimensions. Balloon sinuplasty increased the size of the maxillary ostium and the result was maintained for 12 months after the operation.

Virtual Surgical Planning: Modeling from the Present to the Future.

Virtual surgery planning is a non-invasive procedure, which uses digital clinical data for diagnostic, procedure selection and treatment planning purposes, including the forecast of potential outcomes. The technique begins with 3D data acquisition, using various methods, which may or may not utilize ionizing radiation, such as 3D stereophotogrammetry, 3D cone-beam CT scans, etc. Regardless of the imaging technique selected, landmark selection, whether it is manual or automated, is the key to transforming clinical data into objects that can be interrogated in virtual space. As a prerequisite, the data require alignment and correspondence such that pre- and post-operative configurations can be compared in real and statistical shape space. In addition, these data permit predictive modeling, using either model-based, data-based or hybrid modeling. These approaches provide perspectives for the development of customized surgical procedures and medical devices with accuracy, precision and intelligence. Therefore, this review briefly summarizes the current state of virtual surgery planning.

Graft Materials and Canine Vertical Position Associated with Alveolar Bone Graft Outcomes Assessed by 3D Cone Beam CT

The introduction of Cone Beam Computed Tomography (CBCT) into the alveolar bone grafting protocol now allows surgeons to look at pre- and postoperative bony structures to determine surgical success. Until recently, pre- and postoperative assessment have been determined by 2-dimensional (2D) periapical and panoramic radiographs. CBCTs can now be used to volumetrically assess defects. Yet to date, no scale has been standardized to classify alveolar bone grafting levels postoperatively to determine the success of the procedure. This study aims to analyze pre- and postoperative cone bean CBCT scans to determine if variables such as cleft size, canine position, and bone grafting material can help predict surgical outcomes. A total of 79 patients (average 10.4 years) with non-syndromic complete unilateral cleft lip and palate had been treated with ABG and bone morphogenetic protein-2 with demineralized bone matrix (BMP2/DBM) versus iliac crest bone (ICB) were compared. Preoperative CBCT scans (n = 27) were available to determine the cleft width. The postoperative CBCT was analyzed by the Bergland scale score. A novel method for categorizing canine eruption separated post-graft patients into 5 groups. The cleft width might be correlated with bone graft outcomes, but limited to the sample size, with no statistical significance (n = 27, R2 = 0.378, P > .05). In total, 21 (26.6%) patients have supernumerary or impacted teeth in the cleft, but not related to bone graft outcomes. There is no statistical difference between the 4 surgeons’ cleft repair. The 2D modalities traditionally used to interpret SABG results possess inherent limitations of structure overlapping and distortion of the relationship of anatomy. Since the advent of the CBCT, 3D volumetric analysis has largely accounted for these errors. Yet to date, no scale standardized to the CBCT has been developed to assess SABG results.The authors' results suggest that graft outcomes correlate with pre-graft canine positions. An unerupted, high permanent canine vertical position will yield poor results, likely due to previously documented growth-inhibiting scarring of soft tissue, and the ideal timing of SABG may be when two-thirds of the canine crown is located below the palatal plane with the adjacent premolars not fully erupted. This may be due to the optimal timing for the canine to complete its eruption into the grafting site to influence the maintenance of the graft and periodontal support of the adjacent teeth. In a patient with complete unilateral cleft lip and palate, iliac crest bone graft tended to have better graft outcomes than BMP2/DBM in this sample. This may be attributed to BMP2/DBM's osteoconductive properties vs. ICB's osteogenic, osteoinductive, and osteoconductive properties. There was no evidence that cleft width correlates with the grafting outcome. However, results were limited to sample size.

Stereotactic body radiotherapy for early-stage non-small cell lung cancer: a multicentre study by the Oncologic Group for the Study of Lung Cancer (Spanish Radiation Oncology Society).

Stereotactic body radiotherapy (SBRT) has become the standard of care for patients with medically inoperable early-stage non-small cell lung cancer (NSCLC) and for patients who refuse surgery. The aim of this study was to evaluate the effectiveness and safety of primary SBRT in patients with early-stage NSCLC. Retrospective multicenter study of 397 patients (416 primary lung tumours) treated with SBRT at 18 centres in Spain. 83.2% were men. The median age was 74.4years. In 94.4% of cases, the tumour was inoperable. The pathological report was available in 54.6% of cases. SPSS vs 22.0. was used to perform all statistical analyses. Complete response was obtained in 53.6% of cases. Significant prognostic factors were standard CT planning (p = 0.014) and 4D cone beam CT (p = 0.000). Acute and chronic toxicity ≥ grade 3 was observed in 1.2% of cases. At a median follow-up of 30months, local relapse was 9.6%, lymph node relapse 12.8%, distant metastasis 16.6%, and another lung tumour 11.5%. Complete response was the only significant prognostic factor for local relapse (p = 0.012) and distant metastasis (p = 0.001). The local relapse-free survival was 88.7%. The overall survival was 75.7%. The cancer-specific survival was 92.7%. The disease-free survival was 78.7%. SBRT is an effective and well-tolerated treatment option for patients with early-stage lung cancer who are not suitable for surgery. The most important prognostic factor for local and distant recurrence was complete response, which in our sample depended on the type of CT planning and the IGRT technique.

B-AB04-01 STEREOTACTIC BODY RADIOTHERAPY FOR REFRACTORY SCAR RELATED VENTRICULAR TACHYCARDIA: A SINGLE CENTER EXPERIENCE

Stereotactic body radiation therapy (SBRT) is an emerging treatment option for ventricular tachycardia (VT) refractory to catheter ablation (CA). To describe experience with SBRT for refractory VT with acute and mid-term outcomes. This is a single-center experience of patients who underwent SBRT for VT. The target for therapy was defined based on all available data including 12-lead ECG VT morphology, cardiac imaging, and electroanatomic mapping data. 25 Gy was delivered with 4D CT planning and conebeam CT guidance. All patients were placed on anticoagulation post and had follow up echocardiography and chest CT. A 4-week blanking period was used for VT outcomes. Ten patients with significant scar on cardiac imaging or electroanatomic mapping underwent SBRT; 6 (60%) for VT refractory to treatment, 2 with contraindication to CA, and 2 patients with inaccessible epicardial substrate. 8 (80%) had VT storm. Patients were 62.6±7.8 years, with mean LVEF of 33±14%. All failed antiarrhythmic therapy and amiodarone in 9 (90%) and had 2.2±0.9 prior CA. 9 (90%) had one or more CA at our institution. During a median follow-up of 6.5 months, VT episodes decreased from 44 ± 108 6 months prior to therapy to 4 ± 7 (p = 0.02). ICD shocks decreased from 4.8 ± 3.4 to 0 (p=0.002). 3 (30%) of patients had VT in the first 3 weeks post treatment with no VT after. Two patient deaths occurred in the follow-up period that were unlikely related to SBRT. No short-term complications or changes on ECHO were noted. In patients with VT refractory to medications and CA, SBRT was associated with a marked reduction in VT burden and ICD shocks. Long term outcomes and complications are unknown.

On the evaluation of mobile target trajectory between four-dimensional computer tomography and four-dimensional cone-beam computer tomography.

PurposeFor mobile lung tumors, four‐dimensional computer tomography (4D CT) is often used for simulation and treatment planning. Localization accuracy remains a challenge in lung stereotactic body radiation therapy (SBRT) treatments. An attractive image guidance method to increase localization accuracy is 4D cone‐beam CT (CBCT) as it allows for visualization of tumor motion with reduced motion artifacts. However, acquisition and reconstruction of 4D CBCT differ from that of 4D CT. This study evaluates the discrepancies between the reconstructed motion of 4D CBCT and 4D CT imaging over a wide range of sine target motion parameters and patient waveforms.MethodsA thorax motion phantom was used to examine 24 sine motions with varying amplitudes and cycle times and seven patient waveforms. Each programmed motion was imaged using 4D CT and 4D CBCT. The images were processed to auto segment the target. For sine motion, the target centroid at each phase was fitted to a sinusoidal curve to evaluate equivalence in amplitude between the two imaging modalities. The patient waveform motion was evaluated based on the average 4D data sets.ResultsThe mean difference and root‐mean‐square‐error between the two modalities for sine motion were −0.35 ± 0.22 and 0.60 mm, respectively, with 4D CBCT slightly overestimating amplitude compared with 4D CT. The two imaging methods were determined to be significantly equivalent within ±1 mm based on two one‐sided t tests (p < 0.001). For patient‐specific motion, the mean difference was 1.5 ± 2.1 (0.8 ± 0.6 without outlier), 0.4 ± 0.3, and 0.8 ± 0.6 mm for superior/inferior (SI), anterior/posterior (AP), and left/right (LR), respectively.ConclusionIn cases where 4D CT is used to image mobile tumors, 4D CBCT is an attractive localization method due to its assessment of motion with respect to 4D CT, particularly for lung SBRT treatments where accuracy is paramount.

Evaluation of the setup discrepancy between 6D ExacTrac and cone beam computed tomography in spine stereotactic body radiation therapy.

The objective of this study was to analyze the difference in residual setup errors between 6D ExacTrac and 3D cone-beam computed tomography (CBCT) image-guided systems in spinal stereotactic body radiation therapy (SBRT). We investigated 76 patients with spinal tumors who received SBRT using Novalis Tx at our institution between January 2013 and September 2020. A Vac-lok (EZ-FIX®, Arlico Medical Company, South Korea) fixture and an assistive device, based on the region involved, were used to immobilize patients and to increase the inter-fractional setup reproducibility. The difference in the root mean square (RMS) between the 6D ExacTrac and 3D CBCT was -0.75 mm, 0.45 mm, 0.16 mm, and -0.03°; the RMS value was 1.31 mm, 1.06 mm, 0.87 mm, and 0.64°; and the standard deviation was 0.80 mm, 0.72 mm, 0.62 mm, and 0.44° for lateral, longitudinal, vertical, and yaw directions, respectively. The difference in the average RMS between ExacTrac and CBCT was <1.03 mm in the translation direction and <0.47° in the rotational direction; the results were statistically significant in the lateral, longitudinal, and vertical directions, but not in the yaw direction. Thus, it is necessary to verify the ExacTrac image according to the CBCT image.

The first-in-human implementation of adaptive 4D cone beam CT for lung cancer radiotherapy: 4DCBCT in less time with less dose

Background and purposeWe present the first implementation of Adaptive 4D cone beam CT (4DCBCT) that adapts the image hardware (gantry rotation speed and kV projections) in response to the patient’s real-time respiratory signal. Adaptive 4DCBCT was applied on lung cancer patients to reduce the scan time and imaging dose in the ADaptive CT Acquisition for Personalised Thoracic imaging (ADAPT) trial. Materials and methodsThe ADAPT technology measures the patient’s real-time respiratory signal and uses mathematical optimisation and external circuitry attached to the linear accelerator to modulate the gantry rotation speed and kV projection rate to reduce scan times and imaging dose. For each patient, ADAPT scans were acquired on two treatment fractions and reconstructed with a motion compensated reconstruction algorithm and compared to the current state-of-the-art four-minute 4DCBCT acquisition (conventional 4DCBCT). We report on the scan time, imaging dose and image quality for the first four adaptive 4DCBCT patients. ResultsThe ADAPT imaging dose was reduced by 85% and scan times were 73 ± 12 s representing a 70% reduction compared to the 240 s conventional 4DCBCT scan. The contrast-to-noise ratio was improved from 9.2 ± 3.9 with conventional 4DCBCT to 11.7 ± 4.1 with ADAPT. DiscussionThe ADAPT trial represents the first time that gantry rotation speed and projection acquisition have been adapted and optimised in real-time in response to changes in the patient’s breathing. ADAPT demonstrates substantially reduced scan times and imaging dose for clinical 4DCBCT imaging that could enable more efficient and optimised lung cancer radiotherapy.

Cone-beam computed tomographic analysis of apical transportation and centering ratio of ProTaper and XP-endo Shaper NiTi rotary systems in curved canals: an in vitro study

BackgroundCleaning and shaping of the root canal system is an important step of endodontic treatment. Canal transportation is a common procedural error in preparation of curved canals. This study aimed to compare the canal transportation and centering ratio of two rotary files in curved canals using cone-beam computed tomography (CBCT).MethodsForty-four extracted human mandibular first molars with mature apices and 10° to 30° apical curvature were selected. The samples were randomly divided into two groups (n = 22) with similar curvature. The canals were prepared with ProTaper and XP-endo Shaper file systems according to the manufacturers’ instructions. The CBCT images were obtained using Cranex 3D CBCT scanner before and after root canal preparation, and canal transportation and centering ratio of the files at 3, 4 and 5 mm levels from the apex were calculated. Data were compared between the two groups using independent t-test at 0.05 level of significance.ResultsThe ProTaper Universal caused greater canal transportation and had lower centering ratio than XP-endo Shaper in both mesiodistal and buccolingual directions at all levels from the apex. The difference between the two groups regarding canal transportation was significant at all levels from the apex in buccolingual direction (P < 0.05) except for 3 mm from the apex (P > 0.05). The difference between the two groups regarding centering ratio was not significant (P > 0.05) in mesiodistal direction at all levels except for 4 mm from the apex (P < 0.05).ConclusionThe ProTaper Universal causes greater canal transportation in both buccolingual and mesiodistal directions than XP-endo Shaper.